Field of the Invention
The present invention relates to a liquid crystal display device formed by providing a protective plate or a touch panel on a front surface side of a display panel.
Description of the Background Art
For example, in a liquid crystal display device for outside installation, a transparent protective plate (protective cover) made of a resin or glass is provided on a front surface (display surface) of a display panel for the purpose of protecting the display panel from an outside shock, and the like. In that case, when an air layer exists between the display panel and the protective plate, there occurs a problem in that extraneous light incident from the front surface side of the display panel is reflected on the front and rear surfaces of the protective plate and the front surface of the display panel, to cause deterioration in visibility. Thus, the space between the display panel and the protective plate may be filled with a transparent resin, or the display panel and the protective plate are adhered to each other with a light-transmissive adhesive sheet made of a resin interposed therebetween.
Further, a liquid crystal display device formed by providing a touch panel on a front surface of a display panel also employs a configuration similar to the above so that an air layer is not formed between the touch panel and the display panel.
As thus described, the liquid crystal display device formed by providing the protective plate or the touch panel (hereinafter referred to as “front panel”) on the front surface side of the display panel has the configuration in which the resin layer (injected resin or light-transmissive adhesive sheet) for preventing formation of the air layer is interposed between the display panel and the front panel.
Further, for a liquid crystal display device having a structure in which a front panel is not provided on the front surface side of a display panel, there has been proposed a technique of adjusting a density of columnar spacers that define a cell gap of the display panel for the purpose of preventing display nonuniformity (e.g., Japanese Patent Application Laid-Open No. 2003-287759).
In the liquid crystal display device having the structure in which the front panel such as the touch panel is adhered to the front surface of the display panel (liquid crystal panel) with the resin layer interposed therebetween, there has been a problem in that display nonuniformity is likely to occur in a peripheral part of the liquid crystal panel in a high-temperature environment. This display nonuniformity occurs due to stresses of the liquid crystal panel and the resin layer acting on each other caused by thermal expansion of liquid crystal and the resin layer, and the liquid crystal panel being nonuniformly deformed. In particular, the expanded liquid crystal is likely to flow to the peripheral part of the liquid crystal panel and an amount of the liquid crystal increases in the peripheral part of the liquid crystal panel, thereby causing a cell gap (thickness of the liquid crystal layer) in that portion to become abnormal. This is why display nonuniformity is likely to occur in the peripheral part of the liquid crystal panel.